- Study of 34,000 people finds memory is significantly affected by pollution
- Worst-polluted areas have a decade taken off people's memory
- Cleanest air in England is found on the west coastline
- Subjects were asked to remember a string of 10 words
Research has found people's memory is significantly worse in parts of England with high levels of nitrogen dioxide (NO2) and air particulates (PM10).
The difference in memory quality between England’s cleanest and most-polluted areas is equivalent to the loss of memory from 10 extra years of ageing.
This is consistent with prior smaller-scale laboratory research on rats and other animals. But the new work, by Nick Powdthavee, of Warwick Business School, and Andrew Oswald, of the University of Warwick, is some of the first to confirm the same in humans.
The researchers examined 34,000 English citizens randomly sampled from across England’s local-authority districts. Everyone in the study was asked to remember 10 words in a standardised word-recall test.
The analysis adjusted for a large number of other influences on the quality of people’s memory - including people’s age, health, level of education, ethnicity, and family and employment status.
The report, Is there a link between air pollution and impaired memory? Evidence on 34,000 English citizens, revealing a strong link between air pollution and impaired memory, is to be published in the journal Ecological Economics.
The most polluted air in England is in places like London's Kensington and Islington. The cleanest is on the west coastline in districts like Devon and West Somerset.
Does traffic pollution impair memory?
“There is a little prior evidence of a negative association between levels of traffic pollution and memory using data on elderly individuals and in children,” said Professor Powdthavee.
"But almost all research in human studies on this topic has been based on elementary correlations and not on nationally representative samples of individuals in a country. We have tried to solve these two problems in our study.”
Professor Oswald said: “When it comes to remembering a string of words, a 50 year-old in polluted Chelsea performs like a 60 year-old in Plymouth. We are still not exactly sure how nitrogen dioxide and air particulates act to do this.”
Using a nationally representative sample in the UK Household Longitudinal Study – the Understanding Society – the researchers have been able to study the link between data on a standardised word-recall test that was done in the year 2011 by 34,000 randomly sampled English citizens with data on NO2 and PM10 across 318 geographical areas.
By exploiting regional variations in the direction of prevailing westerly wind and population density as predictors of air pollution but not memory, they were also able to correct for the potential selection effect that might arise from people with impaired memory choosing to live in more polluted areas.
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